1. Field of the Invention
The present invention relates to a method and apparatus suitable for mass production of uniform magnetic head sliders.
2. Description of the Related Art
In a manufacturing process for a magnetic head slider, for example, a magnetic head thin-film is formed on a substrate, and is thereafter subjected to lapping. In this lapping, the heights of a magnetic resistance layer and a gap in the magnetic head thin-film are made constant. The heights of the magnetic resistance layer and the gap are required to have a high accuracy on the order of submicrons. Accordingly, a high working accuracy is required in a lapping apparatus for lapping a row bar as a workpiece.
A conventional magnetic head manufacturing process includes the steps of cutting a wafer to prepare a row bar having a plurality of magnetic head elements arranged in a row, and bonding the row bar to a row tool. This bonding step is carried out by using a bonding apparatus disclosed in Japanese Patent Laid-open No. 10-277469, for example. This bonding apparatus is composed of an adhesive applying mechanism for applying an adhesive in a given amount to the row tool, a mechanism for uniforming the adhesive between the row tool and the row bar, and a presser mechanism for accelerating the curing of the adhesive in the condition where the row tool and the row bar are positioned. In Japanese Patent Laid-open No. 6-349222, there is proposed a method including the steps of bonding a plurality of row bars to a row tool, and thereafter cutting off one of the row bars. However, in this conventional method, the rigidity of the workpiece is reduced with the repetition of the cuffing step, causing an adverse effect on the straightness of the workpiece.
As mentioned above, the magnetic head slider is subjected to lapping so that the height of the magnetic resistance film becomes constant. However, the row bar is very thin such that its thickness is about 0.3 mm. Accordingly, it is difficult to directly lap the row bar by the lapping apparatus, so that the row bar bonded to the row tool is pressed on a lap plate in lapping. During the lapping operation, a resistance in an electrical lapping guide element (ELG element) integrally formed in the row bar is always measured as known in U.S. Pat. No. 5,023,991 and Japanese Patent Laid-open No. 5-123960, for example.
Then, whether or not the height of the magnetic resistance film of each magnetic head element in the row bar has become a target height is detected according to the measured resistance. When it is detected that the magnetic resistance film has been lapped to the target height, according to the measured resistance, the lapping operation is ended. Thereafter, the lapped surface of the row bar is worked to form flying surfaces of a plurality of magnetic head sliders. Then, the row bar is cut into parts having the plurality of magnetic head sliders. Finally, the row tool is heated to melt the adhesive bonding the row bar to the row tool, thereby produce the individual magnetic head sliders.
In this manner, a wafer is first cut to prepare a row bar having a plurality of magnetic head elements arranged in a row, and the row bar is then lapped to thereby allow simultaneous lapping of the magnetic resistance films of the plural magnetic head elements. However, there are variations on the order of submicrons in the height of the magnetic resistance film between the individual magnetic head elements in the row bar, according to the film forming accuracy of the magnetic resistance film or the bonding accuracy of the row bar to the row tool. Accordingly, such variations must be corrected in lapping the row bar, so as to mass-produce magnetic head sliders having uniform characteristics.
Various methods have conventionally been proposed to correct the variations on the order of submicrons in lapping. For example, U.S. Pat. No. 5,607,346 has proposed a method including the steps of forming a plurality of holes in a row tool and respectively applying forces of actuators through the holes to the row tool. However, each actuator is required to have a capability of applying a relatively large force, so as to obtain a desired pressure distribution. Accordingly, it is difficult to manufacture such actuators for applying operational forces to the row tool at multiple points, so that the spacing of these multiple points (holes) cannot be so decreased. As a result, it is difficult to improve the working (lapping) accuracy of the row bar.